Hello Pretty's commission is calculated on the final order total, which includes the cost of the shipping. You'll find that all other marketplaces do the same. There are three reasons for this:
1. We have to pay for it too
Hello Pretty ourselves get charged a transaction fee on the total amount from the banks - they don't discount for the cost of shipping from processing charges, and we pay a percentage of the total amount being processed.
2. Free shipping penalties
If we didn't charge commission on shipping, we would effectively be penalising the designers who subsidise the shipping costs or offer their customers free postage, and
3. Seller abuse, leading to lost customers
If we didn't charge commission on shipping we run the risk of people abusing the system by hiking up their shipping fee and lowering their item price. Besides hurting Hello Pretty as a small business too, it would turn customers away in a hurry, because they hate having to pay extra for shipping.
It's disappointing, but also necessary for those reasons. But if the 15% commission and 5% bank processing fees are too high, there's also the option to upgrade your plan for R99 a month (prepaid, not on a contract) which would mean that you would only pay 3% commission and 5% bank processing fee instead. That works out to a saving of 12%.